my city had about 8000 people protesting under heavy rain last Thursday(20), probably there were many more people but the official numbers are being manipulated (on the other hand, other events, the ones that improve the international image of the country have their numbers increased a lot)
Uh, no they are not. Why not? Because 1: the only government-owned news network didn't cover it at all, and 2: the news-related corporations have been pretty much anti-government since a few reporters got shot with rubber bullets (one of them was shot in the head and had to undergo plastic surgery).
Well, I said probably, they may be correct, but your reasons are not good because the numbers don't come from the media but from the police and/or an specialized institute.
I said they may be manipulated is because other events that covered almost the same area (which is the base for the calculations) got numbers significantly higher, for example some carnival parades got the number of 1 million people while the same area was considered to have 100 thousand people in the protests.
this raises the question of which number is the most correct or both are manipulated
but they may be correct
speaking of the police,
in some of the most peaceful protests the police even marched along with the protesters.
police over-reaction in some protests very probably came from the policemen being scared of the situation (which doesn't justify, but probably was the cause), imagine you having to control 1000 people that may become furious at you. (this is speculation, don't yell at me if I'm wrong, and I don't ignore the cases were the over-reaction had no causes, either way they were wrong)